With an advancement of display technology, an LCD drive speed increases faster and faster, in particular, color sequential display technology and three-dimensional (3D) display technology will have a higher requirement for the update speed of frames (frame rate).
As for the color sequential display technology, red, green, and blue (RGB) lights are used instead of a color filter in the color sequential display. In an orderly manner, an R field is scanned completely, and then the red light is illuminated. Next, a G field is scanned completely, and then the green light is illuminated. Finally, a B field is scanned completely, and then the blue light is illuminated. The RGB lights are illuminated according to the order for achieving the reproduction of colors. However, comparing with a conventional driving method, the conduction duration of a gate line is many times shorter. For example, a conventional frame rate is 60 Hz (for a period about 16.67ms), and the conduction duration of a gate line is about 16.67ms/total number of the gate lines. As for driving the color sequential display technology, the conduction duration of a gate line is about 16.67ms/(number of color field (at least three color field R, S, B)×total number of the gate lines).
While the conduction duration of the gate line is many times shorter than the original conduction duration, a resistance and capacitance delay (RC delay) phenomenon of the gate lines or data lines (source lines) will cause double images of the frame, also known as a ghost image. Referring to FIG. 1, FIG. 1 is a schematic drawing illustrating double images caused by an RC delay of a conventional display device. An example of a display device 10 with a resolution 1600×900 is described, and the display device 10 is utilized to show a frame 100. The display device 10 has a gate driver 200, a plurality of source drivers 300, 1600 vertically aligned data lines (not shown), and 900 horizontally aligned gate lines (not shown).
Referring to FIGS. 1 and 2A, FIG. 2A is a schematic drawing illustrating waveforms of signals for a region A of FIG. 1, where the abscissa represents time, and the ordinate represents signal level. In order to explain clearly, a clock signal (CLK), a data signal (D), a non-delayed scanning signal (S) and a delayed scanning signal (S′) are depicted at different vertical positions. In the region A (indicated by a dashed region at upper right corner of FIG. 1) of the frame 100, the signal of the gate line (scanning signal) is transmitted from the left side to the right side of the display device, so the RC delay at the right side of the frame 100 is more serious. Thus, before the scanning signal of the Nth gate line (N ranges between 1 and 899) has not been completely turned off, the data signal of the (N+1)th gate line has begun to be written into the Nth gate line. Consequently, a liquid crystal capacitor which is located on the Nth gate line is charged by the data signal which should be provided to the (N+1)th gate line. This situation can easily cause an upper double image phenomenon, such as a faint and unclear image above the genuine image “A” shown in FIG. 1.
Referring to FIGS. 1 and 2B, FIG. 2B is a schematic drawing illustrating waveforms of signals for a region B of FIG. 1. In the region B (indicated by a dashed region at lower left corner of FIG. 1), due to a reduction of scanning time, the relationship between the data lines and the gate lines becomes more critical. The RC delay of the data line causes the delay of the data signal transmitted from the top to the bottom of the display device, as indicated by the delayed data signal shown in FIG. 2B for example. The data of the Nth gate line which delays transition is written into the front end of the (N+1)th gate line. This situation can easily cause a lower double image phenomenon, as a faint and unclear image below the current image “B” shown in FIG. 1.
Either the upper double image or the lower double image will cause a viewer discomfort. Therefore, there is a significant need to provide a method for reducing double images of a frame to solve the above-mentioned problems.